RxRPC: Fix the conversion to iov_iter

This commit:

	commit af2b040e
	Author: Al Viro <viro@zeniv.linux.org.uk>
	Date:   Thu Nov 27 21:44:24 2014 -0500
	Subject: rxrpc: switch rxrpc_send_data() to iov_iter primitives

incorrectly changes a do-while loop into a while loop in rxrpc_send_data().

Unfortunately, at least one pass through the loop is required - even if
there is no data - so that the packet the closes the send phase can be
sent if MSG_MORE is not set.
Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/ar-output.c

@@ -548,7 +548,7 @@ static int rxrpc_send_data(struct kiocb *iocb,
 	copied = 0;
 	if (len > iov_iter_count(&msg->msg_iter))
 		len = iov_iter_count(&msg->msg_iter);
-	while (len) {
+	do {
 		int copy;
 
 		if (!skb) {
@@ -689,7 +689,7 @@ static int rxrpc_send_data(struct kiocb *iocb,
 			rxrpc_queue_packet(call, skb, !iov_iter_count(&msg->msg_iter) && !more);
 			skb = NULL;
 		}
-	}
+	} while (len > 0);
 
 success:
 	ret = copied;